// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ipc/ipc_channel.h"

#include <stddef.h>
#include <stdint.h>

#include <limits>

#include "base/atomic_sequence_num.h"
#include "base/rand_util.h"
#include "base/strings/stringprintf.h"
#include "build/build_config.h"

namespace {

// Global atomic used to guarantee channel IDs are unique.
base::StaticAtomicSequenceNumber g_last_id;

} // namespace

namespace IPC {

// static
std::string Channel::GenerateUniqueRandomChannelID()
{
    // Note: the string must start with the current process id, this is how
    // some child processes determine the pid of the parent.
    //
    // This is composed of a unique incremental identifier, the process ID of
    // the creator, an identifier for the child instance, and a strong random
    // component. The strong random component prevents other processes from
    // hijacking or squatting on predictable channel names.
#if defined(OS_NACL_NONSFI)
    // The seccomp sandbox disallows use of getpid(), so we provide a
    // dummy PID.
    int process_id = -1;
#else
    int process_id = base::GetCurrentProcId();
#endif
    return base::StringPrintf("%d.%u.%d",
        process_id,
        g_last_id.GetNext(),
        base::RandInt(0, std::numeric_limits<int32_t>::max()));
}

Channel::OutputElement::OutputElement(Message* message)
    : message_(message)
    , buffer_(nullptr)
    , length_(0)
{
}

Channel::OutputElement::OutputElement(void* buffer, size_t length)
    : message_(nullptr)
    , buffer_(buffer)
    , length_(length)
{
}

Channel::OutputElement::~OutputElement()
{
    free(buffer_);
}

} // namespace IPC
